Perhaps you should try some spelling variations:
nang xuan » nang quan, dang xuan, lang xuan
hieu van » thien van, lieu va, hieu ve
nang xay » dang xay, nganh xay, nang cao
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cam hoc » cao hoc, am hoc, cam hoa
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang xay) OR (nang xuan)) hoi. ((hieu va) or (hieu van)) cam hoc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang xay) OR (nang xuan)) hoi. ((hieu va) OR (hieu van)) cam hoc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang xay) OR (nang xuan)) hoi. ((hieu va) or (hieu van)) cam hoc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang xay) OR (nang xuan)) hoi. ((hieu va) or (hieu van)) cam hoc va hanh vi cua tre*.